The invention relates to safety releases for seat belts, and more particularly to temperature-sensitive bimetal mechanisms for automatically releasing a seat belt fastener.
There are a substantial number of vehicular accidents which occur every year, wherein a vehicle catches fire, usually due to rupture of a fuel tank. In some instances, occupants of the vehicle are trapped inside the vehicle by their seat belts and burn to death because of their inability to release the seat belt fastener. In some instances, the inability of the injured person to release the seat belt fastener is due to injuries sustained by the individual, and other instances to the condition of the victim being in a state of shock or fright. Although consistent use of seat belts has been shown statistically to greatly reduce the number of and seriousness of injuries sustained by vehicle occupants involved in collisions, the fear of being trapped in the vehicle by the seat belt, especially if it catches fire is a strong deterrent to use of seat belts.
A number of automatically separating seat belt fastening devices have been proposed. U.S. Pat. No. 4,014,080 (Caradec) discloses a fastener device in which tablets made of material which disintegrates when heated or submerged in a liquid, initiating movement of an element within the mechanism that releases the seat belt automatically, without necessity of the user to take any action to release the fasteners. The fastener housing is provided with a number of apertures through which water or hot air currents can pass to actuate the device under appropriate conditions. The device is thought to be impractical, and certainly is not easily integrable with a conventional seat belt fastener. U.S. Pat. No. 4,194,764 discloses a complex seat belt coupling device that senses certain stress conditions on the seat belt that might occur during an accident, and then actuates an electronic timer which then automatically releases or disconnects the seat belt after expiration of a predetermined amount of time. This device would be very expensive, and would have to be used in addition to a conventional low cost seat belt fastener.
U.S. Pat. No. 4,532,681 discloses a safety belt coupling device that releases when the temperature rises above a predetermined temperature that causes weakening of a heat-degradable adhesive, such as a solder having a low temperature melting point. U.S. Pat. No. 3,779,004 discloses another type of link including a transverse fusible temperature-responsive link retainer.
Some of the foregoing devices are not reusable after they have been actuated. This can be a disadvantage in hotter parts of the U.S., wherein the interior temperatures in the passenger compartment of an automobile in the summertime often exceed 170.degree. Fahrenheit. Some of the prior devices might be actuated by such high temperatures and thereby be rendered unusable.
None of the above-described devices has the advantage that it can be easily and inexpensively used in conjuntion with and/or incorporated into an ordinary conventional seat belt fastener.
Thus, there remains an unfulfilled need for a very low cost, highly reliable fastening device that can take the place of or be incorporated into a conventional seat belt fastener and give users the security of knowing that the device will automatically release if subjected to high temperatures, such as might be caused by the occurrence of a fire in the vehicle.